Our project has three foci: (1) to characterize the regulation and function of the src family of tyrosine protein kinases (TPK's) in normal hematopoietic cells; (2) to characterize the regulation and function retrovirus-associated diseases such as ATLL; and (3) to utilize TPK inhibitors to block T-cell activation and proliferation signals. We hope to apply the results of these three foci to the treatment of T-cell neoplastic diseases. (1) We have prepared numerous unique biochemical reagents for our studies and have analyzed in detail the expression of c-src, c-yes, fyn, lck, hck, lyn, and c-fgr in hematopoietic cells. The results of these studies have defined the expression of the src family of TPK's in fresh human hematopoietic cells. Protein kinases of the src family, such as lck, have been shown to be important for the generation of IL-2- dependent proliferation signals. Using IL-2-dependent T-cell lines, we further characterized signal transduction pathway(s) initiated by the binding of IL-2 to the high affinity IL-2 receptor. We showed that IL-2-induced signal transduction in T-celis is mediated by p56lck. (2) Recently, we have found that the normal pattern of TPK expression is disrupted in HTLV-I-associated adult T-cell leukemia and lymphoma during the transition from IL-2-dependence to IL-2-independence. The level of p56lck protein is decreased 10-100-fold, with proportional coordinate changes in the expression of 1ck RNA in IL-2-dependent ATLL cell lines, as well as in normal T lymphocytes acutely infected with HTLV-I in vitro. The increased expression of P561yn protein observed in these ATLL cell lines correlates with the increased abunaance of lyn steady-state RNA levels. Preliminary results from several ATLL patients suggest a correlation between the ratio of p56lyc/p56lyn expression and the response to anti-TAC mono-clonal antibody therapy. In normal T-cells, surface protein CD4 is an integral membrane glycoprotein noncovalently associated with the TPK p56lck. We have shown that both HIV-1 and the virus glycoprotein gp 120 fail to elicit detectable p56lck- dependent TPK activation. (3) Deregulation of TPK's has been associated with a number of human cancers, and specific inhibitors of these enzymes are attractive synthetic targets. A number of small molecules have been shown to inhibit the binding of tyrosine-containing substrates to the enzymes. Specific inhibitors of TPK's not only provide useful tools for studying the function of these enzymes but also offer new therapeutic approaches or treatment of certain cancers.